Implement buffer commands :bn, :bp, :bf, :bl

[Manuel T. Schrempf (ManuelTS)]

If I use :b1 - :bxx or :b#, which are already supported, why should I not want to use also :bn, :bp, :bf or :bl? Using other shortcuts or commands in this case would be inconsistent and not vim-like, why should I use ideavim in the first place then when I cannot switch comfortably as in vim between the buffers?

Also, an option would be needed so finally show buffer numbers in the editor tabs.

[Manuel T. Schrempf (ManuelTS)]

I created a PR #1494